Plants of this kind have been known for a long time and, as a general rule, comprise an ingot mold and a secondary cooling device, on a stationary supporting structure, aligned along a casting axis.
The ingot mold consists of a set of walls which are cooled by circulating fluid, which define a bottomless casting cavity and are mounted on a frame-shaped casing which is sufficiently rigid to maintain the positioning of the walls in an accurate manner, it being possible for the latter to be moved, if desired, in order to regulate the dimensions of the casting cavity.
The secondary cooling device itself consists of a set of guiding and cooling devices, generally guiding rolls or plates associated with racks for spraying water, the whole being mounted on a supporting frame and thus defining a passageway placed in the extension of the ingot mold along the casting axis and sometimes known as a "roller apron".
The steel cast into the ingot mold cavity forms, along the cooled walls of the latter, a crust whose thickness increases downwards and which is removed through the opposite end of the cavity, while the cast product, consisting of a liquid core enclosed in the solidified crust, then passes into the guiding jacket whose upper part is placed close to the exit of the ingot mold. The cooling continues inside the guiding jacket whose lower part opens out into a device for extracting the product. The casting may be carried out vertically or in a curved manner, with the roller apron returning to the horizontal the product which is cast vertically.
To enable the product to be readily removed from the ingot mold, the solidified crust must not adhere to the cooled walls and, for this reason, a slight oscillating motion parallel to the axis of casting is applied to the ingot mold. For this purpose, the ingot mold is carried by supporting and guiding members which permit oscillations parallel to the casting axis and are associated with means for controlling oscillations whose amplitude and frequency can be regulated as needed. Since the product is continuous and travels at a substantially constant speed in the roller apron, at each period of oscillating motion, the ingot mold first descends at a speed in relation to that of the product (sinusoidal relationship) down to a certain level, and then rises again to the initial level, while the walls then separate from the product held by the roller apron. To produce this separation, the supporting and oscillating members need therefore to exert a certain force on the ingot mold.
In addition, while continuous casting technology was initially developed for the manufacture of products of relatively small cross-section, it has rapidly been extended to much more substantial plants since, at the present time, slabs more than 2 meters in width and with a thickness of more than 300 mm are being cast continuously. In such cases, the ingot mold reaches a considerable size and weight and the supporting, guiding and oscillation control members must be designed accordingly. In addition, the ingot mold is a sensitive member which must be set accurately and which may be damaged by breakouts of metal, and for this reason it must be capable of being readily taken out of the plant for maintenance or adjustment, or else to be replaced.
It has therefore become customary to make the ingot mold in the form of a separate member which can be fastened removably on a support which is generally plane and is consequently known as the oscillating table, the latter being permanently fastened to the supporting and guiding means which are fastened in places to the plant structure, generally consisting of a metal framework resting on a massive concrete block.
To provide the required degree of freedom when oscillation guidance is provided, a supporting and oscillating lever, which normally comprises two arms placed on each side of the ingot mold, may be connected to the oscillating table by means of two connecting rods articulated, on one side, to the table and, on the other side, to each of the two arms. However, the two arms of the lever may also be articulated directly to the oscillating table, the latter being held by two other connecting rods oriented in directions which are substantially parallel to the two arms of the lever, the precise orientation being determined so that the travel of the ingot mold takes place along the casting axis. The lever and the holding connecting rods are articulated to bearings carried by components which form supporting seats which are placed on and fastened to a stationary platform.
The lever is driven in a reciprocating motion by an oscillation control mechanism which, in most cases, is an eccentric mechanism mounted on the supporting structure at a point which is relatively far from the ingot mold, below the working deck. The forces due to the weight of the ingot mold and to the separation effect, which may be amplified by the levers, are fairly considerable and are absorbed by the bearings of the articulation pivots. These members, generally, are therefore heavy and costly and are subject to relatively high wear because of the high freqency of the oscillating motions and of the applied loads.